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    SubjectRe: [PATCH] staging: comedi: s626: Remove pci-dma-compat wrapper APIs.
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    On 11/07/2020 14:38, Christophe JAILLET wrote:
    > Le 11/07/2020 à 14:35, Suraj Upadhyay a écrit :
    >> The legacy API wrappers in include/linux/pci-dma-compat.h
    >> should go away as it creates unnecessary midlayering
    >> for include/linux/dma-mapping.h APIs, instead use dma-mapping.h
    >> APIs directly.
    >>
    >> The patch has been generated with the coccinelle script below
    >> and compile-tested.
    >>
    >> [...]
    >> @@ expression E1, E2, E3; @@
    >> - pci_alloc_consistent(E1, E2, E3)
    >> + dma_alloc_coherent(&E1->dev, E2, E3, GFP_ATOMIC)
    >>
    >> @@ expression E1, E2, E3; @@
    >> - pci_zalloc_consistent(E1, E2, E3)
    >> + dma_alloc_coherent(&E1->dev, E2, E3, GFP_ATOMIC)
    >
    > This is the tricky part of this kind of cleanup, see below.
    >
    > GFP_ATOMIC can't be wrong because it is was exactly what was done with
    > the pci_ function.
    > However, most of the time, it can safely be replaced by GFP_KERNEL which
    > gives more opportunities to the memory allocator.
    >
    >> [...]
    >> diff --git a/drivers/staging/comedi/drivers/s626.c
    >> b/drivers/staging/comedi/drivers/s626.c
    >> index 084a8e7b9fc2..c159416662fd 100644
    >> --- a/drivers/staging/comedi/drivers/s626.c
    >> +++ b/drivers/staging/comedi/drivers/s626.c
    >> @@ -2130,13 +2130,15 @@ static int s626_allocate_dma_buffers(struct
    >> comedi_device *dev)
    >>       void *addr;
    >>       dma_addr_t appdma;
    >> -    addr = pci_alloc_consistent(pcidev, S626_DMABUF_SIZE, &appdma);
    >> +    addr = dma_alloc_coherent(&pcidev->dev, S626_DMABUF_SIZE, &appdma,
    >> +                  GFP_ATOMIC);
    >>       if (!addr)
    >>           return -ENOMEM;
    >>       devpriv->ana_buf.logical_base = addr;
    >>       devpriv->ana_buf.physical_base = appdma;
    >> -    addr = pci_alloc_consistent(pcidev, S626_DMABUF_SIZE, &appdma);
    >> +    addr = dma_alloc_coherent(&pcidev->dev, S626_DMABUF_SIZE, &appdma,
    >> +                  GFP_ATOMIC);
    >>       if (!addr)
    >>           return -ENOMEM;
    >>       devpriv->rps_buf.logical_base = addr;
    > 's626_allocate_dma_buffers()' is only called from 's626_auto_attach()'.
    > In this function, around the call to 's626_allocate_dma_buffers()', you
    > can see:
    >   - a few lines before, a call to 'comedi_alloc_devpriv()'
    >
    >   - a few lines after, a call to 'comedi_alloc_subdevices()'
    >
    > These 2 functions make some memory allocation using GFP_KERNEL.
    >
    > So it is likely that using GFP_KERNEL in your proposal is also valid.

    Indeed, GFP_KERNEL is perfectly fine here. It could be done as a
    follow-up patch, or done in a v2 of this patch with a mention in the
    patch description.

    --
    -=( Ian Abbott <abbotti@mev.co.uk> || Web: www.mev.co.uk )=-
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